The influence of iron oxidation state on quantitative MRI parameters in post mortem human brain
Christoph Birkl,
Anna Maria Birkl-Toeglhofer,
Christian Kames,
Walter Goessler,
Johannes Haybaeck,
Franz Fazekas,
Stefan Ropele,
Alexander Rauscher
Affiliations
Christoph Birkl
UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada; Department of Neuroradiology, Medical University of Innsbruck, Austria; Department of Neurology, Medical University of Graz, Austria; Corresponding author. UBC MRI Research Centre, University of British Columbia, M10 - Purdy Pavilion, 2221 Wesbrook Mall, Vancouver, BC, V6T 2B5, Canada.
Anna Maria Birkl-Toeglhofer
Department of Pathology, Neuropathology and Molecular Pathology, Medical University of Innsbruck, Austria; Diagnostic and Research Institute of Pathology, Medical University of Graz, Austria
Christian Kames
UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada; Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada
Walter Goessler
Institute of Chemistry, Analytical Chemistry, University of Graz, Austria
Johannes Haybaeck
Department of Pathology, Neuropathology and Molecular Pathology, Medical University of Innsbruck, Austria; Diagnostic and Research Institute of Pathology, Medical University of Graz, Austria
Franz Fazekas
Department of Neurology, Medical University of Graz, Austria
Stefan Ropele
Department of Neurology, Medical University of Graz, Austria
Alexander Rauscher
UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada; Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada; Department of Pediatrics (Division of Neurology), University of British Columbia, Vancouver, BC, Canada
A variety of Magnetic Resonance Imaging (MRI) techniques are known to be sensitive to brain iron content. In principle, iron sensitive MRI techniques are based on local magnetic field variations caused by iron particles in tissue. The purpose of this study was to investigate the sensitivity of MR relaxation and magnetization transfer parameters to changes in iron oxidation state compared to changes in iron concentration. Therefore, quantitative MRI parameters including R1, R2, R2∗, quantitative susceptibility maps (QSM) and magnetization transfer ratio (MTR) of post mortem human brain tissue were acquired prior and after chemical iron reduction to change the iron oxidation state and chemical iron extraction to decrease the total iron concentration. All assessed parameters were shown to be sensitive to changes in iron concentration whereas only R2, R2∗ and QSM were also sensitive to changes in iron oxidation state. Mass spectrometry confirmed that iron accumulated in the extraction solution but not in the reduction solution. R2∗ and QSM are often used as markers for iron content. Changes in these parameters do not necessarily reflect variations in iron content but may also be a result of changes in the iron’s oxygenation state from ferric towards more ferrous iron or vice versa.
